This invention relates to xerographic image fusing and, in particular, to apparatus and method for effecting image fixing by placing an image bearing support material in thermal contact with a bath of liquid metal.
In the process of xerography, a xerographic plate comprising a layer of photoconductive insulating material placed on a conductive backing is given a uniform electic charge over its surface. The charged photoconductor is then exposed to a light image of the subject matter to be reproduced thereby discharging the photoconductive plate in the areas of greatest radiation intensity to create an electrostatic latent image. The latent image is developed with an electrostatically charged finely divided powder or toner which is brought into contact with the photoconductive layer. The toner is electrostatically attracted to the image areas thus developing the latent image. Thereafter, the developed xerographic powder image is electrostatically transferred to a support material to which it is fixed to form a permanent copy. One way in which the toner image is fixed to the support material is by heat fusing. All of this is well known in the art.
One method of heat fusing a toner image is disclosed in U.S. Pat. Application Ser. No. 459,863, filed Apr. 11,1974 by Prafulla S. Dhoble. The full disclosure of the Dhoble application is incorporated herein by reference.
In brief, the Dhoble invention is of a method and apparatus for heat fusing a toner image by immersion of the support material and toner image in a hot liquid, including certain molten metals. Basically, the unfused toner image is driven on a web of paper through a bath of molten metal which fuses the toner to the paper. This is shown schematically in FIG. 1 of the drawing. While the liquid metal does not wet the paper, minute particles of the metal may get embedded in the paper or in the fused image. Furthermore, oxidation of the molten metal exposed to atmosphere is undesirable.
It is an object of this invention, therefore, to provide a method and apparatus for xerographic fusing by means of a liquid metal in which embedding of metal particles in the toner or in the support material is avoided.
Another object of this invention is to provide a method and apparatus for xerographic fusing by the application of liquid metal with means to prevent the metal from oxidizing.
Briefly, the salient features of this invention include xerographic fusing by moving a support material and an undeveloped xerographic image thereon through a liquid metal bath. A layer of molten plasticizer floats atop the liquid metal whereby paper flowing into the system is contacted and coated by the placticizer prior to contact with the liquid metal. The layer of plasticizer coats the entire copy and xerographic image to prevent particles of the liquid metal from attaching thereto, and also serves as an oxidation barrier for the liquid metal.
For a better understanding of this invention, reference is made to the following detailed description given in connection with the accompanying drawing.